This invention relates to new gas separation membranes fabricated from copolymers containing a hydrocarbon backbone and pendant (hydrocarbylamido)alkyl ester moieties. This invnetion further relates to a method of separating gases using the novel membranes herein disclosed.
Membranes have been used to separate a variety of different gases, including hydrogen, helium, oxygen, nitrogen, carbon dioxide, methane, and light hydrocarbons. Particular applications of interest include obtaining an enriched oxygen stream from air for enhanced combustion or for increasing the efficiency of fermentation processes. Other applications include using membranes to obtain an enriched nitrogen stream from air for inert padding of flammable fluids or for food storage. Membranes may also be used in the separation of carbon dioxide and light hydrocarbons as part of the tertiary oil recovery process.
To separate a gas mixture, the gaseous components are contacted with one side of a semipermeable membrane through which at least one of the gaseous components selectively permeates. A gaseous component which selectively permeates through the membrane passes through the membrane more rapidly than the other component(s) of the mixture. The gas mixture is thereby separated into a portion which is enriched in the selectively permeating component(s) and a portion which is depleted in the selectively permeating component(s). A portion of the gas mixture which is depleted in the selectively permeating component(s) is enriched in the nonpermeating component(s). A non-permeating component permeates more slowly through the membrane than the other component(s). The membrane material is chosen so that some degree of separation of the gas mixture can be obtained.
Membranes have been fabricated from a wide variety of polymeric materials. An ideal gas separation membrane possesses a high separation factor, high gas permeability, and good mechanical properties. Polymers possessing high separation factors (selectivities) generally have undesirably low permeabilities. Those polymers having high permeabilities generally have low separation factors. In the past, a choice between a high gas permeability and a high separation factor has been required. There is a present need to develop a membrane which possesses all three desired characteristics.